Window adapter for portable box fans



FIG. 1 is a perspective view;

FIG. 2 is a front view;

FIG. 3 is a left side view;

FIG. 4 is a right side view; and,

FIG. 5 is a top, view, the bottom being a mirror image of that shown. 

The ornamental design for a window adapter for portable box fans, as shown and described. 